A particulate mass measurement device can employ an elastic element and a connected particulate matter collector, which may be a filter. The mass measurement device operates by measuring changes in frequency based on mass loading. Namely, the elastic element and the collector are made to oscillate at a resonant frequency that changes with particulate mass loading onto the collector. Exemplary construction and operation of such a mass measurement device are disclosed in U.S. Pat. Nos. 3,957,469 and 4,391,338 assigned to the same assignee as this application, which patents are hereby incorporated herein by reference in their entirety. Other, tuning fork type inertial mass measurement devices are disclosed in Japanese patent publications JP 2-161323 and JP 2-324364.
Often, the mass measurement device is employed under changing ambient temperatures. In order to measure mass accurately, such a device usually requires careful control of the temperature of the elastic element and the filter.
Hence, a common practice is to hold the temperature of the elastic element and the filter at a very steady value above the highest expected ambient temperature. However, this practice requires disadvantageously large energy expenditures at low ambient temperatures. Such energy expenditures would require unsuitably large batteries in, for example, portable instruments. Furthermore, if the elastic element and the filter are held at a temperature too high above a certain transitory ambient temperature, then the character of sample mass collected can be adversely altered.
One known configuration for measurement of mass which reduces error due to temperature change of the elastic element employs a technique of bringing as close to zero as possible the temperature coefficient of elastic modulus of the elastic element. In particular, the composition of elastic glass members is altered in order to produce a near-zero temperature coefficient of elastic modulus. Such an arrangement is disclosed in U.S. Pat. No. 4,855,260 to Dumbaugh, Jr. et al. (entitled "Glasses Exhibiting Low Thermal Coefficients of Elasticity," issued Aug. 8, 1989, and assigned to Corning Incorporated). Undesirably, this production of near-zero temperature coefficient of elastic modulus employs processes which are expensive in terms of labor, material, and time. Further, an inertial balance can include the elastic element plus a substrate surface upon which mass is deposited. However, the earlier design does not address effects of the substrate surface on the overall temperature coefficient. Should a formation of the substrate surface or its equivalent contribute a significant component to temperature response of the inertial balance, mass measurement performance of the inertial balance would fail to be optimized.
Thus, a need exists for a mass measurement device having an elastic element and a mass holder, where the device has enhanced accuracy of mass determination in the presence of changing temperature, while reducing or eliminating the need for active temperature control for the device.